1. Field of the Invention
The present invention relates to magnetic-tape recording apparatuses and methods, magnetic-tape formats, and recording media, and more particularly, to a magnetic-tape recording apparatus and method, a magnetic-tape format, and a recording medium which allow high-quality video data to be recorded into a magnetic tape.
2. Description of the Related Art
Compression technologies have been advancing these days. Video data is compressed, for example, by a Digital Video (DV) method and recorded into a magnetic tape. The format therefor is specified as a DV format for commercial digital video tape recorders.
FIG. 1 shows the structure of one track in the conventional DV format. In the DV format, 24-to-25 conversion is first applied to video data, and then the data is recorded. The number of bits in each portion shown in FIG. 1 is obtained after 24-to-25 conversion.
The substantial zone of one track corresponds to a wrapping angle of 174 degrees of a magnetic tape. An overwrite margin 1,250 bits long is formed outside the zone of the track. The overwrite margin is for preventing data to be deleted from remaining after deletion.
The length of the zone of one track is 134,975 bits when a rotating head is rotated at a frequency of 60×1000/1001 Hz, and is 134,850 bits when the rotating head is rotated at 60 Hz.
In a track, an insert-and-track-information (ITI) sector, an audio sector, a video sector, and a sub-code sector are sequentially disposed in a direction in which the rotating head traces (in the direction from the left to the right in FIG. 1). A gap G1 is formed between the ITI sector and the audio sector, a gap G2 is formed between the audio sector and the video sector, and a gap G3 is formed between the video sector and the sub-code sector.
The ITI sector is 3,600 bits long. At the beginning therefor, a pre-amble 1,400 bits long used for generating a clock is formed. A start sync area (SSA) and a track information area (TIA) are next formed with a length of 1,920 bits. The SSA has a bit string (sync number) required for detecting the TIA position. The TIA includes information indicating a commercial DV format, information indicating an SP mode or an LP mode, and information indicating the pattern of a pilot signal in one frame. A post-amble 280 bits long is disposed next to the TIA.
The gap G1 is 625 bits long.
The audio sector is 11,550 bits long. A pre-amble is disposed at the first 400 bits thereof, and a post-amble is disposed at the last 500 bits thereof. Data (audio data) is disposed at the area therebetween, which is 10,650 bits long.
The gap G2 is 700 bits long.
The video sector is 113,225 bits long. A pre-amble is disposed at the first 400 bits thereof, and a post-amble is disposed at the last 925 bits thereof. Data (video data) is disposed at the area therebetween, which is 111,900 bits long.
The gap G3 is 1,550 bits long.
The sub-code sector is 3,725 bits long when the rotating head is rotated at a frequency of 60×1000/1001 Hz, and is 3,600 bits long when the rotating head is rotated at 60 Hz. A pre-amble is disposed at the first 1,200 bits thereof, and a post-amble is disposed at the last 1,325 bits (when the rotating head is rotated at a frequency of 60×1000/1001 Hz) or at the last 1,200 bits (when the rotating head is rotated at 60 Hz) thereof. Data (sub-code) is disposed at the area therebetween, which is 1,200 bits long.
In the DV format, the gaps G1 to G3 are formed between the ITI sector, the audio sector, the video sector, and the sub-code sector as described above, and in addition, a preamble and a post-amble are formed in each sector. Therefore, so-called overheads are long and a sufficient recording rate cannot be obtained for substantial data.
To record high-quality video data (hereinafter called high-definition (HD) video data), for example, a bit rate of about 25 Mbps is required. In the conventional recording method, the video rate corresponding to an MP@HL Moving Picture Expert Group (MPEG) method is at most about 24 Mbps except for the rate of search-image data. As a result, standard-quality video data (hereinafter called standard-definition (SD) video data) can be recorded, but it is impossible to compress and record HD video data by the MP@HL or an MP@H-14 method.